Polyembryony

Polyembryony is a form of asexual reproduction. In seed plants so that the formation is characterized by several embryos in a seed plant or in a seed. This loose definition includes several different kinds of formation of embryos. In animals, this indicates the formation of monozygotic multiple pregnancies.

Botany

In the actual Polyembryony the embryos arise all from a single zygote. This often occurs in gymnosperms. In this case, however, usually only one embryo develops until maturity.

Next there is sporophytic polyembryony at which the embryos develop from the tissues of the maternal sporophyte, from the nucellus or the integument, or from the zygote, the proembryo or suspensor from cells. Gametophytic Polyembryonen arise from other cells of the embryo sac as the egg. These are the synergids or antipodal cells.

In Pinus and some Podocarpaceae, the suspensor is split into four parts, so that four embryos arise. In Gnetum there are several oocytes and zygotes thus per ovule, additional embryos arise from each zygote by branching of the primary and the secondary suspensors. Usually, however, only a mature embryo develops per seed. With Ephedra, the zygote divides three times, from the resulting eight cells usually develop three to five embryos.

In angiosperms occurs Polyembryony on in many families. In the genus Citrus she performs regularly, in some species in nearly every ovule. Adventitious, arising from the nucellus, the Nucellarembryonie, are more likely than those from the integument. It occurs in many dicots and some monocots ( Liliaceae, Amaryllidaceae, Orchidaceae, Araceae, Poaceae ). Integument embryos occur predominantly in dicots, monocots only under the Liliaceae and Amraryllidaceae. Known examples of polyembryony are next to Citrus Mangifera, Opuntia, Nicotiana, Funkia, Lilium, Erythronium, Allium and Poa.

As Pseudopolyembryonie is the formation of an embryo each of several ova or embryo sacs in an ovule. This is known as of Trifolium, pink and Saxifraga.

Zoology

The zygote divides into a very early stage in mehrzelligem one or more daughter nuclei. They are genetically identical.

Polyembryony occurs in some invertebrates such as bryozoans, earthworms, some species of parasitic wasps in armadillos, and occasionally in other mammals as well as humans. This results in monozygotic multiple births.

Documents

• Arthur J. Eames: Morphology of the Angiosperms. McGraw- Hill, New York 1961, pp. 345-347. (no ISBN ) ( Botany)
• Scherf, Gertrud: Dictionary biology. dtv, 1997. ISBN 3-423-32500-3
• West Heath, W.; Rieger, R.: Systematic Zoology. Part 1 protozoa and invertebrates. Gustav Fischer Verlag, Stuttgart, Jena, New York, 1996 ISBN 3-437-20515-3